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Thread: A luddite approach to the eclipse today

  1. #1
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    Default A luddite approach to the eclipse today



    Doing things with minimalist equipment can be a badge of honor. Somehow, the less gear I use, the more satisfied I am with being witness to a natural event.

    It's been years since I made a pinhole box for viewing the sun. Last week I was about to recycle a small box, but instead I decided to keep it to store small tools for the scope. Then today, I looked at that box and decided to do it again. Then a little tinfoil taped over a hole, a pinhole in the tinfoil, and a pause to wait for the clouds to clear. Here's the first image, clearly showing the beginning of the eclipse on one edge. Notice that the view is from the side, peeking through a crack in the lid, so there is some distortion of the apparent shape of the sun.

    If you are viewing this post within a couple of hours of upload, it's not too late for you to do the same thing.

    The other good news is that I can still use the box (grin).AX3F0037 eclipse.jpgAX3F0034first.jpgAX3F0036peep.jpg
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    Dave
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    Default Re: A luddite approach to the eclipse today

    Dang, I was hoping for one more image of this. But with low cloud and a bit of rain, that's looking less likely. Looking at the very diminished sun through cloud and my full manual welding helmet, I can see the dark area to the left of the sun and lighter area to the upper right, almost a red sunset appearance projected onto the clouds on the right. It's quite a bit cooler here now than it was a couple of hours ago.
    Dave
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    Default Re: A luddite approach to the eclipse today

    I went with the simple method today also. :-)

    Here's my version...
    eclipse.jpg
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    Default Re: A luddite approach to the eclipse today

    I missed it due to clouds, but I do appreciate your minimalist approach! Well done!
    -John

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    Default Re: A luddite approach to the eclipse today

    Quote Originally Posted by excelsior84 View Post
    I went with the simple method today also. :-)

    Here's my version...
    eclipse.jpg
    On any forum, I find the most illuminating posts are those that spark imagination. Excelsior84, After I saw your little pinhole camera made with only a thumb and forefinger, I spent some minutes at Wikipedia, on the topic of camera obscura and pinhole cameras. My first instinct was that the aperture was too large for the focal distance and "shutter" thickness. But with the huge f ratio these devices have, the latitude for focus is broad. Was the image of your eclipse inverted and backward? Your photo reminds me of what happens when you stand under trees during an eclipse. If the gaps between leaves is just right, you get hundreds of little eclipse images projected onto the ground. Just for fun I think I might make a 'whole room' Camera Obscura from a covered window in a dark room, to see the inverted image of the world projected onto the opposite wall.
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    Default Re: A luddite approach to the eclipse today

    Quote Originally Posted by spelunkerd View Post
    On any forum, I find the most illuminating posts are those that spark imagination. Excelsior84, After I saw your little pinhole camera made with only a thumb and forefinger, I spent some minutes at Wikipedia, on the topic of camera obscura and pinhole cameras. My first instinct was that the aperture was too large for the focal distance and "shutter" thickness. But with the huge f ratio these devices have, the latitude for focus is broad. Was the image of your eclipse inverted and backward? Your photo reminds me of what happens when you stand under trees during an eclipse. If the gaps between leaves is just right, you get hundreds of little eclipse images projected onto the ground. Just for fun I think I might make a 'whole room' Camera Obscura from a covered window in a dark room, to see the inverted image of the world projected onto the opposite wall.
    :-) Yes, it was! Truth be told I was quite surprised it worked, but as it happened, more through dumb luck than through planning, with the sun at 30 degrees in the sky and being about 6 foot tall, it comes out to something around 12 feet of focal distance, or 144 inches, so you want an inch and a half aperture, roughly, to hit the desired f/100, and that is about what my hands make naturally. There were some leaf projected eclipse images around as well, but there are mostly palm trees, which don't work so well for the purpose. :-)

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    Default Re: A luddite approach to the eclipse today

    Quote Originally Posted by excelsior84 View Post
    :-) Yes, it was! Truth be told I was quite surprised it worked, but as it happened, more through dumb luck than through planning, with the sun at 30 degrees in the sky and being about 6 foot tall, it comes out to something around 12 feet of focal distance, or 144 inches, so you want an inch and a half aperture, roughly, to hit the desired f/100, and that is about what my hands make naturally. There were some leaf projected eclipse images around as well, but there are mostly palm trees, which don't work so well for the purpose. :-)
    OK, now I'm officially confused. I just used that Petzval formula, taken off the Wikipedia article of pinhole cameras, as follows. d=sqrt(2*f*lambda), where f= distance from aperture to focal plane, d= diameter of optimal aperture, and lambda is the wavelength of the light (average 550 nm). Using that method, the optimal aperture for best resolution at the focal plane is 2mm (!). However I get your crafty use of f100, which I believe is conventional for such a camera, and easier math. Presumably the wider aperture gives better light and a bigger image at the focal plane. Maybe because there is no darkness, better light wins out even if optimal focus would favour a smaller aperture....
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    Default Re: A luddite approach to the eclipse today

    Yeah, I can't reconcile it with the Petzval formula either, as I get the same. Maybe as you suggest, 2mm *would* give the sharpest focus, but you have a lot of room to be out of focus...? Of course the formula gives an optimal focal length for that aperture on the order of a third of a mile and an f ratio of around f/10,000. :P Have to give this more consideration later.

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